QCD Axion-Mediated Dark Matter

TL;DR

This paper investigates how a QCD axion with a decay constant below 10^11 GeV can mediate interactions between the Standard Model and dark matter, influencing dark matter relic abundance through freeze-out and freeze-in mechanisms.

Contribution

It introduces a novel framework where a QCD axion mediates dark matter interactions, providing new insights into dark matter relic density and experimental prospects.

Findings

Axion can significantly affect dark matter relic abundance.

QCD axion-mediated interactions enable freeze-out and freeze-in scenarios.

Framework offers predictive experimental targets.

Abstract

A QCD axion with a decay constant below $ 10 ^{ 11} ~{\rm GeV} $ is a strongly-motivated extension to the Standard Model, though its relic abundance from the misalignment mechanism or decay of cosmic defects is insufficient to explain the origin of dark matter. Nevertheless, such an axion may still play an important role in setting the dark matter density if it mediates a force between the SM and the dark sector. In this work, we explore QCD axion-mediated freeze-out and freeze-in scenarios, finding that the axion can play a critical role for setting the dark matter density. Assuming the axion solves the strong CP problem makes this framework highly predictive, and we comment on experimental targets.